In some cases (not necessarily steelhead), reducing drastically reducing bag limits, adopting catch and release regulations and banning angling methods that cause high release mortality can dramatically increase abundance and angling success. All that's been done with steelhead in BC.
Except for the fact that 99% of those changes were done long before the time period in the study you provided. If we check our regulations from the last 12 years, we will find that basically nothing has been changed from 2012-2024.
So basically, we have the same regulations, with a sharp drop in angler effort and fish landed.....and still....the returns continue to diminish....